The long term goal of this research is to identify the technical, relational, and contextual mechanisms of change in the treatment of specific psychological disorders, and to facilitate the translation of these findings into the validation and dissemination of efficacious treatments. The specific aim of the proposed study is to understand a proposed mechanism of change in psychotherapy for Borderline Personality Disorder (BPD) through examination of the relationship between alliance and outcome in two well established treatments for BPD. The project seeks to answer three foundational questions regarding the alliance in BPD: 1) do treatment differences exist in the formation of early alliance in line with emphasis on supportive and validating techniques early in treatment? 2) is alliance predictive of treatment retention/termination in this population? And 3) do patient and therapist contributions to the alliance both uniquely predict treatment outcome in BPD? Unlike previous studies of alliance, observer ratings will be used rather than patient or therapist report in order to compensate for existent difficulties with these two sources of data. Archival data from ninety patients randomized to one of three treatments (DBT, TFP, or Supportive psychotherapy (SPT)) and had outcome assessed five times through the treatment year, will be utilized. Alliance will be assessed with the Working Alliance Inventory - Observer version (WAI) at two early sessions (within the first 2 months of treatment). It is hypothesized that working alliance will be higher in individuals treated with DBT and SPT than TFP. It is also hypothesized that working alliance will be predictive of early termination, such that lower alliance will be associated with early termination and higher alliance will be associated with treatment retention. Finally, it is predicted that both the therapist's and the patient's contribution to alliance will be predictive of outcome. BPD is a costly, painful, debilitating, and deadly disorder, and thus represents a serious clinical and public health concern. Across multiple studies of Axis I psychopathology, alliance has been shown to be a robust predictor of outcome. In addition, formation of a alliance is considered crucial in theoretical descriptions of the treatment of BPD. However, little systematic research has been conducted to determine the empirical status of this relationship. The maximization of efficacy in the treatment of BPD depends upon understanding the specific mechanisms that characterize the disorder and that determine clinical change. Through direct investigation of the alliance in a well controlled study of treatments for BPD, important questions regarding the role of alliance in therapeutic change with this population can be answered.